2205 (UNS S32205) Duplex Stainless Steel Coil Tube
1. Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. offers a premium-grade 2205 Duplex Stainless Steel Coil Tube (UNS S32205), engineered for demanding industrial environments where superior mechanical strength, exceptional corrosion resistance, and structural integrity are paramount. As a standard-grade duplex austenite-ferrite stainless steel, this coil tube combines the best attributes of both austenitic and ferritic stainless steels, delivering approximately twice the yield strength of conventional 304/316 austenitic grades while maintaining outstanding resistance to chloride-induced pitting and crevice corrosion.
The 2205 duplex coil tube is a leading solution in high-pressure heat exchangers, desalination equipment, and oil and gas pipeline systems worldwide. Its balanced microstructure—comprising roughly 50% austenite and 50% ferrite—ensures excellent weldability, thermal fatigue resistance, and long service life under aggressive chemical and thermal conditions.
2. Material Composition & Properties
2.1 Chemical Composition (wt%)
| Element | Specification | Typical Range |
|---|---|---|
| Chromium (Cr) | 22.0 – 23.0% | 22.0% |
| Nickel (Ni) | 4.5 – 5.5% | 5.0% |
| Molybdenum (Mo) | 3.0 – 3.5% | 3.0% |
| Nitrogen (N) | 0.14 – 0.20% | 0.15% |
| Carbon (C) | ≤ 0.030% | ≤ 0.025% |
| Manganese (Mn) | ≤ 2.0% | ≤ 1.0% |
| Silicon (Si) | ≤ 1.0% | ≤ 0.5% |
| Sulfur (S) | ≤ 0.030% | ≤ 0.015% |
| Titanium (Ti) | ≤ 0.70% | ≤ 0.40% |
2.2 Corrosion Resistance Index
The Pitting Resistance Equivalent Number (PREN) of 2205 duplex stainless steel is calculated as follows:
PREN = %Cr + 3.3 × %Mo + 16 × %N ≈ 34 – 38
This PREN value significantly exceeds that of 316L austenitic stainless steel (PREN ≈ 24–26), placing 2205 among the most corrosion-resistant standard-grade stainless steels available. It provides superior protection against chloride stress corrosion cracking (Cl-SCC), pitting, and crevice corrosion in seawater, brine, and acidic process environments.
2.3 Mechanical Properties
| Property | Specification (Annealed Condition) |
|---|---|
| Tensile Strength (UTS) | ≥ 550 MPa (80 ksi) |
| Yield Strength (0.2% Offset) | ≥ 450 MPa (65 ksi) |
| Elongation (at fracture) | ≥ 25% |
| Hardness (Brinell) | ≤ 310 HBW |
| Density | 7.8 g/cm³ |
| Thermal Conductivity (at 25°C) | 18 W/m·K |
| Thermal Expansion Coefficient (10–100°C) | 13.0 × 10⁻⁶ /°C |
| Maximum Service Temperature | 300°C (572°F) |
3. Product Specifications
| Parameter | Specification |
|---|---|
| Product Name | Duplex Stainless Steel Coil Tube (2205 / S32205) |
| Material Standard | ASTM A790 / ASTM A790M, EN 10216-5, NACE MR0175 |
| UNS Designation | S32205 |
| Equivalent Grades | SAF 2205, 1.4462, 03Cr22Ni5Mo3N, UNS S31803 (variant) |
| Tube Outer Diameter (OD) | 6.0 mm – 108.0 mm (adjustable per order) |
| Wall Thickness | 0.5 mm – 6.0 mm |
| Coil Length | Custom (typically 50 m – 300 m per coil) |
| Surface Finish | BA (Bright Annealed), 2B, No.4 Brushed, or Custom |
| Tolerance (OD) | ±0.10 mm or per ASTM A790 |
| Tolerance (Wall Thickness) | ±10% or per ASTM A790 |
| End Condition | Plain end, beveled end, or capped (as required) |
| Delivery Form | Coiled (Coiltube) — ready for tube drawing or heat exchanger bundling |
| PREN Value | 34 – 38 |
4. Manufacturing Process
The production of 2205 duplex stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage metallurgical process:
- Raw Material Selection: Virgin duplex steel slabs or strip are sourced from certified mills meeting ASTM A790 chemical composition requirements, with nitrogen content carefully controlled during the heat treatment stage.
- Hot Rolling & Annealing: The steel strip is hot-rolled to the target dimensions, followed by solution annealing at 1050–1100°C to achieve a balanced austenite-ferrite phase ratio (~50/50) and eliminate residual stresses.
- Cold Rolling: The annealed strip is cold-rolled to precise wall thickness specifications, inducing beneficial strain hardening while maintaining dimensional accuracy.
- Coil Forming & Welding: The flat strip is formed into a tube shape and longitudinally welded using Automatic Argon Arc Welding (A-TIG / 6GT) with inert gas shielding to prevent oxidation and ensure a high-quality weld seam.
- Post-Weld Annealing: The welded coil tube undergoes a final solution anneal (1050–1100°C) followed by rapid water quenching to restore the duplex microstructure and optimize corrosion resistance and mechanical properties.
- Precision Sizing & Straightening: The coil tube passes through a multi-roller sizing mill to achieve final OD and wall thickness tolerances.
- Surface Treatment: Pickling and passivation (or bright annealing in a controlled atmosphere) are performed to remove mill scale, oxide layers, and surface contaminants, ensuring a clean, corrosion-resistant surface.
- Quality Inspection & Coiling: Each coil undergoes ultrasonic testing (UT), eddy current inspection, hydrostatic pressure testing, and visual examination before final coiling and packaging.
5. Applications
The 2205 duplex stainless steel coil tube is the material of choice for the following demanding applications:
- High-Pressure Heat Exchangers: The superior yield strength (≥450 MPa) enables thinner wall designs at elevated operating pressures, reducing weight and cost while maintaining safety margins. The duplex microstructure resists thermal fatigue cycling.
- Desalination Equipment: Exceptional resistance to chloride-induced pitting and crevice corrosion makes 2205 ideal for seawater intake systems, reverse osmosis (RO) pretreatment, multi-stage flash (MSF) distillation units, and brine handling in desalination plants.
- Oil & Gas Pipelines: Meets NACE MR0175/ISO 15156 requirements for sour service environments containing hydrogen sulfide (H₂S), carbon dioxide (CO₂), and chlorides. Used in wellhead equipment, subsea pipelines, and process piping.
- Chemical Processing: Suitable for reactors, condensers, and heat exchangers handling aggressive chemical media including chlorinated organics, acids, and alkaline solutions.
- Marine & Offshore Engineering: Applied in offshore platform piping, ballast water systems, and marine heat exchangers where resistance to seawater corrosion is critical.
- Power Generation: Used in flue gas desulfurization (FGD) systems, economizers, and cooling water circuits in thermal power plants.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. ensures full traceability and compliance through the following certifications and testing protocols:
- Material Certificates: EN 10204 Type 3.1 mill test certificates (MTC) provided for every batch, documenting chemical composition, mechanical properties, and heat treatment records.
- Standards Compliance: ASTM A790/A790M, EN 10216-5, ASME B31.3, NACE MR0175/ISO 15156, API 5L (where applicable).
- Non-Destructive Testing (NDT): 100% ultrasonic testing (UT) for wall thickness and internal defects; eddy current testing (ECT) for surface and near-surface flaw detection; dye penetrant testing (PT) for weld seam integrity.
- Destructive Testing: Tensile testing, impact testing (Charpy V-Notch), and hardness testing performed per ASTM E8, ASTM E23, and ASTM E10 respectively.
- Hydrostatic Pressure Testing: Each coil tube section is pressure-tested to verify weld seam integrity and dimensional conformance.
- ISO 9001:2015: Quality management system certification ensuring consistent product quality and process control throughout manufacturing.
- Third-Party Inspection: Available upon request through internationally recognized inspection bodies (e.g., TÜV, DNV, Lloyd's Register, Bureau Veritas).
7. Unique Selling Points
- Exceptional Strength-to-Weight Ratio: Approximately 2× the yield strength of 304/316 austenitic stainless steels, enabling lighter, more compact designs at high pressures.
- Outstanding Chloride Corrosion Resistance: PREN of 34–38 provides superior protection against pitting, crevice corrosion, and chloride stress corrosion cracking (Cl-SCC) compared to standard austenitic grades.
- Cost-Effective Alternative to Super Duplex: Delivers near-super-duplex performance at a fraction of the material cost, offering an optimal balance of performance and economics.
- Excellent Weldability: The balanced duplex microstructure allows reliable field and shop welding with standard procedures, minimizing weld-affected zone sensitization.
- Wide Temperature Range: Suitable for cryogenic applications down to −40°C and elevated temperatures up to 300°C without significant property degradation.
- Custom Coil Configuration: Available in a broad range of OD, wall thickness, and coil lengths tailored to specific heat exchanger tube bundle or pipeline requirements.
- Full Traceability & Certification: Complete documentation from raw material to finished product ensures compliance with global engineering and regulatory standards.